title: Hypoxic challenge test applied to healthy children: influence of body positions and exertion on pulse oximetric saturation.
abstract: BACKGROUND
  Commercial aircraft are pressurised to ~2438 m (8000 ft) above sea level that equates breathing 15% oxygen at sea level. A preflight hypoxic challenge test (HCT) is therefore recommended for children with cystic fibrosis or other chronic lung diseases and inflight oxygen is advised if pulse oximetric saturation (SpO2) decreases <90%.
  
  
  OBJECTIVE
  Study responses to a modified HCT, encompassing various body positions and light physical activity, reflecting relevant activities of children during flight, with a view to challenge the evidence of the current cut-off.
  
  
  METHODS
  Oxygenation, heart rate and ventilation were observed in 34 healthy schoolchildren (17 boys) undergoing a modified HCT, alternating between breathing room air and 15% oxygen in nitrogen while seated, supine, standing and walking at 3 km/h and 5 km/h.
  
  
  RESULTS
  Nadir SpO2 <90%, median (range), occurred in 9 subjects sitting, 89% (78-89%); 6 supine, 88.5% (87-89%); 9 standing, 89% (85-89%); 23 walking 3 km/h, 87% (74-89%); and 21 walking 5 km/h, 86% (74-89%). Total time <90% for these subjects in seconds was 20 (10-80) sitting, 30 (10-190) supine, 50 (10-150) standing, 80 (10-260) walking 3 km/h and 125 (10-300) walking 5 km/h. Light exercise in general led to lower SpO2: 91% (77-96%), p<0.0001.
  
  
  CONCLUSIONS
  A modified HCT led to moments of desaturation below 90% in various body positions at rest and during light physical activity in healthy schoolchildren. It is questionable whether the international recommended cut-off of 90% for children with chronic lung disease reflects clinical oxygen dependence during flights.
authors.affiliation: Paediatric Pulmonary Service, Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Helene Elgaard
authors.initials: HE
authors.lastname: Kobbernagel
authors.forename: Kim Gjerum
authors.initials: KG
authors.lastname: Nielsen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Hanel
mesh_terms: D000293:Adolescent; D017732:Air Ambulances; D000531:Altitude; D002648:Child; D002908:Chronic Disease / Q000628:therapy*; D018592:Cross-Over Studies; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008171:Lung Diseases; D008297:Male; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D013147:Spirometry; D011795:Surveys and Questionnaires
chemical_list: D010100:Oxygen